Corrosion resistant cemented carbide for fluid handling

ABSTRACT

A cemented carbide for fluid handling components or a seal ring has a composition in wt %; about 7-11 Ni; about 0.5-2.5 Cr 3 C 2 ; and about 0.5-1 Mo; and a balance of WC, with an average WC grain size greater than or equal to 4 μm.

TECHNICAL FIELD/INDUSTRIAL APPLICABILITY

The present disclosure relates to cemented carbides for flow components, and more particularly to fluid handling components such as seal rings having improved service life.

BACKGROUND

Seal rings are the key critical component in mechanical shaft seals for pumps where corrosion resistance is an issue. Cemented carbides show a good mechanical performance in this kind of application.

Similarly, cemented carbide flow components, the primary function of which is to control the pressure and flow of well products, are used in, for example, the oil and gas industry where components are subjected to high pressures of multi-media fluid where there is a corrosive environment. A cemented carbide grade with Ni—Cr—Mo binder having improved corrosion resistance for use in choke valves is disclosed in WO2012/045815, also assigned to the assignee of the present disclosure

One of the most important properties for seal rings is thermal conductivity. This is crucial for seal rings because during the operation of a pump the friction between the seal rings generates heat. This heat needs to be conducted away; otherwise the heat will lead to a temperature increase in the sealing gap, which again can lead to evaporation of the lubricating film and dry running. Point temperatures of over 300° C. can be reached during seal ring dry running. Thus, the thermal conductivity of the seal ring material is vitally important in dissipating the temperature generated. Materials with low thermal conductivities tend to fail prematurely in service due to thermal cracking. Therefore, there is still a need for a type or grade of cemented carbide having high thermal conductivity and high corrosion resistance.

SUMMARY

It is an aspect of the present disclosure to provide a cemented carbide for fluid handling components and for a seal ring, all of which having improved corrosion resistance.

The present disclosure therefore provides a cemented carbide composition for fluid handling components and/or seal rings comprises in wt % about balance WC; about 7-11 Ni; about 0.5 to 2.5 Cr₃C₂; and about 0.5 to about 2.5 Mo.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter further comprises of from 0.3 to 1.5 wt % Nb.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 8.0 to about 10.1 wt % Ni.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 8.0 to about 9.0 wt % Ni, such as 8.49 wt %

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 9.1 to about 10.1 wt % Ni, such as 9.6 wt %

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.7 to about 1.0wt % Cr₃C₂.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.7 to about 0.9 wt % Cr₃C₂, such as 0.8 wt %

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.8 to about 1.0 wt % Cr₃C₂, such as 0.9 wt %.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.7 to about 1.0wt % Mo.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.7 to about 0.9 wt % Mo, such as 0.8 wt %.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 0.8 to about 1.0 wt % Mo, such as 0.9 wt %.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 88.0 to about 90.6 wt % WC.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 87.9 to about 89.1 wt % WC, such as 88.6 wt %.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition comprising from about 89.4 to about 90.5 wt % WC, such as 89.91 wt %

In an embodiment, the composition as defined hereinabove or hereinafter has an average grain size of from about 4 μm to about 10 μm, such as 8 μm.

In an embodiment, a cemented carbide for a fluid handling component or seal ring as defined hereinabove or hereinafter, has a composition comprising in wt %: of 89.91% WC; of 8.49 Ni; of 0.8 Cr₃C₂; and of 0.8 Mo, wherein the composition has an average grain size equal to or greater than 4 μm.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a composition has a density of about 14.3 to about 14.7 g/cm³, such as about 14.4 to about 14.6 g/cm³.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a density of from 14.4 to 14.6 g/cm3.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a hardness of from 1000 to 1100 HV30.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a toughness of from 10 to 13 MPa·√m.

In an embodiment, a cemented carbide for a fluid handling component or seal ring as defined hereinabove or hereinafter, the cemented carbide having a composition comprising in wt % of 88.6% WC; of 9.6 Ni; of 0.9 Cr₃C₂; and of 0.9 Mo, wherein the composition has an average WC grain size greater than 4 μm.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has an average WC grain size of 8 μm.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a hardness of about 990 HV30.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a toughness of about 12.2 MPa·√m.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a density of 14.4 g/cm³.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has an average WC grain size of 4 μm.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a hardness of 1290 HV30.

In an embodiment, the cemented carbide composition as defined hereinabove or hereinafter has a toughness of about 11.6 MPa·√m.

The foregoing summary, as well as the following detailed description of the embodiments, will be better understood when read in conjunction with the appended drawings. It should be understood that the embodiments depicted are not limited to the precise arrangements and instrumentalities shown.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an SEM image of an embodiment of cemented carbide for a flow component or seal ring.

FIG. 2 is an SEM image of another embodiment of cemented carbide for a flow component or a seal ring.

FIG. 3 is an SEM image of another embodiment of cemented carbide for a flow component or a seal ring.

FIG. 4 is an SEM image of another embodiment of cemented carbide for a flow component or a seal ring.

DETAILED DESCRIPTION

As used herein, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used. Therefore, about 50% means in the range of 45%-55%.

As will be described fully herein, embodiments of the present disclosure relate to cemented carbides for flow components (herein, the term “component” means parts or pieces), particularly for seal rings used in the oil and gas industry, where the components are subjected to high pressures of multi-media fluid and where there is a corrosive environment. Under severe conditions of multi flow media; these components may suffer from extreme mass loss by exposure to solid particle erosion, acidic corrosion erosion-corrosion synergy and cavitation mechanisms even when fitted with cemented carbide trims.

Seal rings are the key critical component in mechanical shaft seals for pumps. The seal rings act as barriers in pumps (i.e., to separate liquids and confine pressure) by preventing leakage and excluding contamination. Cemented carbide shows a good mechanical performance in this kind of application.

The cemented carbide seal rings of the present disclosure have improved application relevant properties, such as improved corrosion resistance. The carbon content within the sintered cemented carbide should be kept within a narrow range in order to retain a high resistance to corrosion and wear, as well as have a high toughness. The carbon level of the sintered structure is held in the lower portion of the range between free carbon in the microstructure (top limit) and eta-phase initiation (bottom limit).

Conventional powder metallurgical methods, such as (but not limited to) milling, drying, pressing, shaping, sintering and sinter hipping, which are used for manufacture of conventional cemented carbides are used to manufacture embodiments of the present disclosure.

A cemented carbide for seal rings (CR) according to an embodiment the present disclosure has a composition in weight percent % of about balance WC; 7-11 Ni; 0.5-2.5 Cr₃C₂; and Mo of about 0.5 to about 2.5.

It should be appreciated that the following examples are illustrative, non-limiting examples. The compositions and results of the embodiments are shown in Tables 1 and 2 below.

EXAMPLES

TABLE 1 Ref A B C Sample CR seal ring CR seal ring CR seal ring WC 88.6 88.6 89.91 WC grain size (μm) 4 8 8 TiC (wt %) 0 0 0 Co (wt %) 0 0 0 Ni (wt %) 9.6 9.6 8.49 Mo (wt %) 0.9 0.9 0.8 Cr₃C₂ (wt %) 0.9 0.9 0.8

TABLE 2 Ref A B C Sample CR seal CR seal ring CR seal ring ring Density (gm/cm³) 14.4 14.4 14.4-14.6 Hardness (Hv30) 1290 990 1000-1100 Toughness (K1c) 11.6 12.2 10.0-13.0 In the examples below the powders were sourced from the following suppliers: (W,Ti)C from Zhuzhou or HC Starck, Co from Umicore or Freeport, Ni from Inco, Mo from HC Starck and Cr₃C₂ from Zhuzhou or HC Starck

Example 1

A cemented carbide grade with the composition in wt-% of about 88.6 WC; about 0.9 Cr₃C₂; about 0.9 Mo; and about 9.6 Ni was producing using WC powder with an average FSSS (Fisher Sub Sieve Sizer) particle size (d50) of greater than about 0.5 μm, for example, about 4 to about 8. The cemented carbide samples were prepared from powders forming the hard constituents and powders forming the binder. The powders were wet milled together with lubricant and anti-flocculating agent until a homogeneous mixture was obtained and granulated by drying. The dried powder was pressed on the Tox press to bodies and ‘green machined’ before sintering. Sintering was performed at 1360-1410° C. for about 1 hour in vacuum, followed by applying a high pressure, 50 bar Argon, at sintering temperature for about 30 minutes to obtain a dense structure before cooling. The sintered structure is shown in FIG. 1 with a grain size of 0.8 μm.

Referring to Table 2, with WC grain size of about 4 μm has a hardness HV30 of about 1290 and a toughness of K1C 11.6 MPa·√m. With WC grain size of about 8 μm the harness HV30 is about 990 and the toughness K1C IS 12.2 MPa·√m. It can be observed that when the coarser raw material is used (4 or 8 μm) the hardness is reduced and the toughness increased. FIG. 2 is an SEM image of the sintered structure with a grain size of 4 μm. FIG. 3 is an SEM image of the sintered structure with a grain size of 8 μm.

Example 2

A cemented carbide grade with the compositions in wt-% of about 89.91 WC; about 0.8 Cr₃C₂; about 0.8 Mo; and about 8.49 Ni and was produced using WC powder with an average FSSS particle size (d₅₀) of greater than about about 4 μm and/or about 8 μm. The cemented carbide samples were prepared from powders forming the hard constituents and powders forming the binder. The powders were wet milled together with lubricant and anti-flocculating agent until a homogeneous mixture was obtained and granulated by drying. The dried powder was pressed on the Tox press to bodies and ‘green machined’ before sintering. Sintering was performed at 1360-1410° C. for about 1 hour in vacuum, followed by applying a high pressure, 50 bar Argon, at sintering temperature for about 30 minutes to obtain a dense structure before cooling. The sintered structure with a grain size of 8 μm is shown in FIG. 4.

The composition mentioned has the following properties: density: 14.4-14.6 g/cm3; hardness HV30: 1000-1100 and toughness K1C: 10-13 MPa·√m. The grades disclosed herein demonstrate improved corrosion resistance in comparison to a standard seal ring grade. Corrosion resistance was determined using a modified test to ASTM G61. ASTM G61 covers a procedure for conducting potential dynamic polarization measurements. The modification of this standard has been in the media used. Instead of using 3.5% NaCl solution in the tests, artificial seawater according to ASTM D1141 was used as the media. Furthermore, the flushed port cell used in ASTM G61 was replaced by sealing the specimen with epoxy to avoid crevice corrosion on the edge of the sample. The pitting potential was used as a measure for comparison. The higher the value, the better is the corrosion resistance of the material. The value measured for a standard seal ring grade was Epit=263 mV SCE. However, for the above CR grade the Epit=443 mV SCE showing improved corrosion resistance.

As discussed supra, one of the key properties for seal rings is thermal conductivity. One way to increase thermal conductivity is to increase the average WC grain size. Thermal conductivity was measured between a cemented carbide grade of 88.6% WC, 9.6% Nicke1,0.9% Cr₃C₂ and 0.9% Mo having an average WC grain size of 0.8 μm. As shown in Table 3 below, the higher the grain size the higher the thermal conductivity.

TABLE 3 Thermal conductivity (W/(mK)) Temperature (° C.) Choke valve grade A Room temperature 46 85 200 53 80 401 53 72 1000 55 62

Itemized List of Embodiments

1. A cemented carbide for a fluid handling component or seal ring, the cemented carbide having a composition comprising in wt %:

-   -   a balance of WC;     -   of 7-11 Ni;     -   of 0.5-2.5 Cr₃C₂; and     -   of 0.5-2.5 Mo,     -   wherein the composition has an average WC grain size greater         than 4 μm.

2. The cemented carbide of item 1, wherein the composition further comprises of from 0.3 to 1.5 wt % Nb.

3. The cemented carbide of items 1 or 2, wherein the composition has an average grain size of 8 μm.

4. A cemented carbide for a fluid handling component or seal ring, the cemented carbide having a composition comprising in wt %:

-   -   of 89.91% WC;     -   of 8.49 Ni;     -   of 0.8 Cr₃C₂; and     -   of 0.8 Mo,     -   wherein the composition has an average grain size greater than 4         μm.

5. The cemented carbide of item 4, wherein the composition has an average grain size of 8 μm.

6. The cemented carbide of item 4 or 5, wherein the composition has a density of from 14.4 to 14.6 g/cm³.

7. The cemented carbide of any of items 4-6, wherein the composition has a hardness of from 1000 to 1100 HV30.

8. The cemented carbide of any of items 4-7, wherein the composition has a toughness of from 10 to 13 MPa·√m.

9. A cemented carbide for a fluid handling component or seal ring, the cemented carbide having a composition comprising in wt %:

-   -   of 88.6% WC;     -   of 9.6 Ni;     -   of 0.9 Cr₃C₂; and     -   of 0.9 Mo,     -   wherein the composition has an average WC grain size greater         than 4 μm.

10. The cemented carbide of item 9, wherein the composition has an average WC grain size of 8 μm.

11. The cemented carbide of items 9 or 10, wherein the composition has a hardness of from 990 HV30.

12. The cemented carbide of any of items 9-11, wherein the composition has a toughness of from 12.2 MPa·√m.

13. The cemented carbide of any of items 9-12, wherein the composition has a density of from 14.4 g/cm³.

14. The cemented carbide of item 9, wherein the composition has an average WC grain size of 4 μm.

15. The cemented carbide of item 9 or 14, wherein the composition has a hardness of from 1290 HV30.

16. The cemented carbide of any of items 9, 14 or 15, wherein the composition has a toughness of about 11.6 MPa·√m.

Although the present embodiments have been described in relation to particular aspects thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present embodiment(s) be limited not by the specific disclosure herein, but only by the appended claims. 

1. A cemented carbide for a fluid handling component or seal ring, the cemented carbide having a composition comprising in wt % (weight %): a balance of WC; about 7-11 Ni; about 0.5-2.5 Cr₃C₂; and about 0.5-2.5 Mo, wherein the composition has an average WC grain size greater than or equal to 4 μm.
 2. The cemented carbide of claim 1, wherein the composition further comprises of from about 0.3 to about 1.5 wt % Nb.
 3. The cemented carbide according to claim 1, wherein the composition comprises from about 8.0 to about 10.1wt % Ni.
 4. The cemented carbide according to claim 3, wherein the composition comprises of from about 8.0 to about 9.0 wt % Ni.
 5. The cemented carbide according to claim 3, wherein the composition comprises of from about 9.1 to about 10.1 wt % Ni.
 6. The cemented carbide according to claim 1, wherein the composition comprises from about 0.7 to about 1.0wt % Cr₃C₂.
 7. The cemented carbide according to claim 6, wherein the composition comprises from about 0.7 to about 0.9 wt % Cr₃C₂.
 8. The cemented carbide according to claim 6, wherein the composition comprises from about 0.8 to about 1.0 wt % Cr₃C₂.
 9. The cemented carbide according to claim 1, wherein the composition comprises from about 0.7 to about 1.0wt % Mo.
 10. The cemented carbide according to claim 9, wherein the composition comprises from about 0.7 to about 0.9 wt % Mo.
 11. The cemented carbide according to claim 9, wherein the composition comprises from about 0.8 to about 1.0 wt % Mo.
 12. The cemented carbide according to claim 1, wherein the composition comprises of from about 87.9 to about 90.6 wt % WC.
 13. The cemented carbide of claim 12, wherein the composition comprises of from about 87.9 to about 89.1 wt % WC
 14. The cemented carbide of claim 12, wherein the composition comprises of from about 89.4 to about 90.6 wt % WC
 15. The cemented carbide according to claim 1, wherein the composition has a density of about 14.3 to about 14.7 g/cm³.
 16. The cemented carbide according to claim 1, wherein the composition has an average grain size of greater than or equal to about 4 to about 10 μm. 